Allow new gesture scroll during snap animation
This patch fixes the issue in the linked bug by having InputHandler
de-latch at the start of a snap animation rather than at the end.
This allows a new gesture to latch onto a different scroll node
while the previous scroll node's snap animation is in progress.
In the unit test TrackAnimatingSnapTargetIds, a ScrollBegin call is
added to eschew violating the last_latched_scroll_type_ DCHECK[1] in
InputHandler::ScrollLatchedScroller.
Bug: 333708040
Change-Id: I7571a09644433ebea051a994935a987fdb25e704
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5826968
Reviewed-by: Steve Kobes skobes@chromium.org
Commit-Queue: David Awogbemila awogbemila@chromium.org
Cr-Commit-Position: refs/heads/main@{#1377084}